1. Field of the Invention
This invention relates in general to a tool for assembling fastener pins and fastener collars on workpieces, and particularly relates to an assembly for expelling spent or severed pintails from the interior of the tool.
2. Description of Prior Developments
A known fastener system marketed by Huck Manufacturing Company under the tradename HUCKBOLT includes a headed fastener pin having a number of axially spaced circumferential grooves formed therein. The pin is adapted to extend through aligned holes in a pair of facially engaged workpieces so that the head of the pin is engaged against one face of the workpiece assembly and the grooved portion of the pin extends beyond the other face of the workpiece assembly. A fastener collar is placed over the grooved portion of the pin, after which a fastener tool is operated to swage the collar into the circumferential grooves. The workpiece assembly is thus sandwiched between the head of the pin and the fastener collar.
The collar-swaging operation is performed with a reciprocating tool that includes a pin puller jaw mechanism movable in one direction, and an annular anvil movable in the opposite direction so that the anvil can move over the surface of the fastener collar to radially compress the collar material into the circumferential grooves in the fastener pin.
The fastener pin has a relatively deep break neck groove that forms a weak point at an intermediate point along the pin length. As the anvil completes the swaging stroke the pin puller jaw mechanism exerts an increased axial force on the pin so that the pin breaks at the break neck groove. As the pin breaks, the pin puller jaw mechanism moves rapidly away from the main body portion of the pin to carry the severed stub portion of the pin into a bore extending into the interior space of the tool. The severed pin portion, sometimes termed a pintail, develops significant axial momentum as it travels with and then separates from the jaw mechanism.
In some tool constructions an ejector mechanism is included for the purpose of absorbing some of the pintail momentum and dislodging and ejecting the pintail from the tool after the pin-severing action. One conventional ejector mechanism includes an elongated rod slidably positioned in a bore in the pin puller actuator structure. A coil spring is arranged in the bore to axially bias the ejector rod toward the open front end of the bore.
The pintail impacts axially against the ejector rod to move it rearwardly into the bore as the coil spring compresses to absorb some of the pintail momentum and energy. The compressed spring then recoils to drive the rod in the reverse direction to eject the pintail from the pin puller jaw mechanism.
During the reciprocating motion of the ejector rod, the interior end of the rod may forcibly strike against an end wall at the bottom of the bore. A considerable impulse or shock force is thereby generated in the rod, leading to a reduced service life and possible fracture of the rod. The present invention is aimed at reducing these shock forces, thereby effectively increasing the service life and reliability of the ejector rod.